Method and arrangement for optically monitoring a driver of a vehicle in which a portion of the driver is illuminated with electromagnetic radiation in an infrared portion of the electromagnetic spectrum using at least one illumination device, images of the illuminated driver are obtained using at least one image obtaining device and the images are analyzed to derive a measure of flow of blood in at least one blood vessel, capillary and vein in the face of the occupant. The blood flow over time is analyzed to determine whether the driver has lost the ability to continue to control the vehicle. The loss of ability to continue to control the vehicle exemplifies the driver becoming drowsy, falling asleep or otherwise being incapable of controlling the vehicle after initially having been awake or otherwise capable of controlling the vehicle.
